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result(s) for
"Li, Mei-Qi"
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Public services and agglomeration effect under spatial structure: Threshold verification on the provincial capital cities in China
This paper explains the relationship between public services expenditure and agglomeration economy from the perspective of spatial structure, considering that the allocation of public service expenditure by local governments does not fully leverage the benefits of agglomeration effects. We constructed a general equilibrium model that examines the close relationship between public service expenditure and agglomeration effect. From a spatial structure perspective, regions are categorized into monocentric and polycentric spatial structures. We discussed the scale of urban expansion and the level of public service expenditure in secondary cities across these different types of spatial structures. It was examined 31 provincial capitals of China as research samples to validate the applicability of theoretical mechanism analysis. Six models were constructed using 2S-GMM to investigate the relationship between the public service expenditure and agglomeration effect. Meanwhile, the PTR method was employed to develop 36 models to assess the threshold effect of urban expansion scale and public service expenditure in the second city of the region, focusing on the influence mechanism of public service expenditure allocation on the agglomeration effect. Three noteworthy conclusions are as follows: (1) the scale and structure of public service expenditure has a positive influence on agglomeration effect. (2) in monocentric structure areas, we should focus on the impact of the public services expenditure structure on agglomeration effect in the changes of urban scale. (3) in polycentric structure areas, we should focus on the impact of the public services expenditure structure on agglomeration effect in the changes of scale of public services in the second central city. This research not only have enhanced the theoretical influence mechanism of public service expenditure on the agglomeration effect from the perspective of spatial structure, but also offers guidance on the allocation of public service expenditure in provincial capital cities.
Journal Article
Emigration and fiscal gap in population-exporting region
This paper analyzes how emigration impacts fiscal gap of population-exporting region in the long term. We construct a general equilibrium model of emigration and fiscal gap and make empirical verification using two-step system GMM model. Among the major lessons from this work, five general and striking results are worth highlighting: (1) the economic losses of emigration are the immediate cause of widening the fiscal gap. (2) in the short and long term, emigration can expand the fiscal revenue gap through the superimposed effect of tax rate and tax base. (3) the gap in fiscal expenditure is widened by the outflow of people in the short term. However, local governments would change the strategy to keep the spending gap from widening in the long run. (4) a positive impact of emigration on the fiscal gap. the more severe population emigration, the larger the fiscal gap. (5) when the trend of emigration becomes irreversible, the subsequent efforts of local governments to expand fiscal expenditure for attraction population would not only fail to revive the regional economy, but aggravate the expansion of fiscal gap. The contribution of research is twofold. On the one hand, it fills the theoretical gap between emigration and fiscal gap because previous studies have paid little attention to the fiscal problems of local government of population outflow. On the other hand, the selection of Northeast China that has been subject to long-term out-of-population migration is good evidence to verify this theory, which is tested very well using the 2S-GMM model. The comprehensive discussion on the relationship between emigration and fiscal gap is helpful to guide those continuous population-exporting regions that are facing a huge fiscal gap how to solve the fiscal gap and unsustainability from the perspective of fiscal revenue and expenditure.
Journal Article
Use of computed tomography-derived body composition to determine the prognosis of patients with primary liver cancer treated with immune checkpoint inhibitors: a retrospective cohort study
Background
Immune checkpoint inhibitors (ICIs) have been used to successfully treat primary liver cancer (PLC); however, identifying modifiable patient factors associated with therapeutic benefits is challenging. Obesity is known to be associated with increased survival after ICI treatment; however, the relationship between body composition (muscle, fat) and outcomes is unclear. This study aimed to evaluate the association between sarcopenia and CT-derived fat content and the prognosis of ICIs for the treatment of PLC.
Methods
In this retrospective cohort study of 172 patients with PLC, we measured the skeletal muscle index (SMI), skeletal muscle density, visceral adipose tissue index, subcutaneous adipose tissue index, total adipose tissue index (TATI), and visceral-to-subcutaneous adipose tissue area ratio using CT. In addition, we analyzed the impact of body composition on the prognosis of the patients. Multivariate Cox regression analysis was used to screen for influencing factors.
Results
Among the seven body composition components, low SMI (sarcopenia) and low TATI were significantly associated with poor clinical outcomes. Multivariate analysis revealed that sarcopenia (hazard ratio [HR], 5.39; 95% confidence interval [CI], 1.74–16.74;
p
= 0.004) was a significant predictor of overall survival (OS). Kaplan–Meier curves showed that sarcopenia and TATI were significant predictors of OS. Body mass index was not associated with survival outcomes.
Conclusions
Sarcopenia and fat tissue content appear to be independently associated with reduced survival rates in patients with PLC treated with ICIs.
Journal Article
MOF-derived the direct Z-scheme g-C3N4/TiO2 with enhanced visible photocatalytic activity
In order to produce a photocatalyst with increased visible photocatalytic ability, MIL-125 and melamine were selected as raw materials to prepare Z-scheme g-C
3
N
4
/TiO
2
heterojunction photocatalyst using a simple calcination method. TEM, HRTEM, XRD, FTIR, EDS, and UV–vis absorption spectra were employed to investigate the prepared specimens. The visible-light catalytic property was examined via the degradation of methylene blue (MB). The recombination and separation activity of electrons and holes (h
+
/e
−
) were explored by the transient photocurrent response (TPR) and PL spectra. In contrast with plain TiO
2
and g-C
3
N
4
, the g-C
3
N
4
/TiO
2
photocatalyst exhibited increased photocatalytic activities when exposed to visible-light irradiation. With the addition of g-C
3
N
4
at 8 wt%, the Z-scheme g-C
3
N
4
/TiO
2
heterojunction performed best in the photocatalytic test toward MB dye at a degradation rate of 97.7%. Under visible-light irradiation, the Z-scheme heterojunction between g-C
3
N
4
and TiO
2
enables the high-efficient segregation of photogenic electrons and holes (h
+
/e
−
), leading to the increased photocatalytic ability. Meanwhile, the large specific surface area of the composite photocatalyst is conducive to the adsorption of the contaminant on the catalyst surface, which has an important effect on the catalytic reaction.
The direct Z-scheme g-C
3
N
4
/TiO
2
was obtained by an in-situ heat treatment process with MIL-125 (Ti) and melamine as raw materials. The g-C
3
N
4
/TiO
2
photocatalyst with 8 wt% g-C
3
N
4
exhibited the optimal degradation efficiency, which was due to the high separation efficiency of photogenic electrons and holes (h
+
/e
−
) of the Z-scheme heterojunction.
Highlights
MOF-derived direct Z-scheme g-C
3
N
4
/TiO
2
heterojunction photocatalyst was prepared.
The g-C
3
N
4
/TiO
2
heterojunction photocatalyst with an amount of 8 wt% g-C
3
N
4
has the best degradation efficiency.
Journal Article
Fabrication and X-ray microtomography of sandwich-structured PEEK implants for skull defect repair
Bone defects pose a significant risk to human health. Medical polyetheretherketone (PEEK) is an excellent implant material for bone defect repair, but it faces the challenge of bone osteoconduction and osseointegration. Osteoconduction describes the process by which bone grows on the surface of the implant, while osseointegration is the stable anchoring of the implant achieved by direct contact between the bone and the implant. Bone defects repair depends on the implant’s three-dimensional spatial structure, including pore size, porosity, and interconnections to a great extent. However, it is challenging to fabricate the porous structures to meet specific requirements and to characterize them without causing damage. In this study, we designed and fabricated sandwich-like PEEK implants mimicking the three-layer structures of the skull, whose defects imposes a significant burden on young adulthood and paediatric populations, and performed in-line phase-contrast synchrotron X-ray microtomography to non-destructively investigate the internal porous microstructures. The sandwich-like three-layer microstructure, comprising a dense layer, a loose layer and a dense layer in succession, exhibits structural similarity to that in a natural skull. This work demonstrated the fabrication of the sandwich-like PEEK implant that could potentially enhance osteoconduction and osseointegration. Furthermore, the interior structures and residual porogen sodium chloride particles were observed within the PEEK implant, which cannot be realized by other microscopic methods without destroying the sample. It highlights the advantages and potential of using synchrotron X-ray microtomography to analyze the structure of biomedical materials. This study provides theoretical guidance for the further design and fabrication of PEEK bone repair materials and will advance the clinical application of innovative bioactive bone repair materials.
Journal Article
Mechanical Response Analysis of Low-Temperature Modified Asphalt Pavement Based on Finite Element Simulation Models
An asphalt pavement model was established using ABAQUS finite element simulation software. Based on the dynamic modulus of low-temperature modified asphalt mixtures, mechanical response analyses were performed on pavement models with different surface course materials. The influence patterns of low-temperature modified asphalt mixture surface courses on the tensile strain at the bottom of the asphalt layer, surface vertical displacement, and tensile stress at the bottom of the base course were investigated. The optimal combination was determined to be an upper surface course of AC-13 USP-SBS asphalt mixture and a lower surface course of AC-20 SBS asphalt mixture.
Journal Article
High-altitude hypoxia exposure inhibits erythrophagocytosis by inducing macrophage ferroptosis in the spleen
High-altitude polycythemia (HAPC) affects individuals living at high altitudes, characterized by increased red blood cells (RBCs) production in response to hypoxic conditions. The exact mechanisms behind HAPC are not fully understood. We utilized a mouse model exposed to hypobaric hypoxia (HH), replicating the environmental conditions experienced at 6000 m above sea level, coupled with in vitro analysis of primary splenic macrophages under 1% O 2 to investigate these mechanisms. Our findings indicate that HH significantly boosts erythropoiesis, leading to erythrocytosis and splenic changes, including initial contraction to splenomegaly over 14 days. A notable decrease in red pulp macrophages (RPMs) in the spleen, essential for RBCs processing, was observed, correlating with increased iron release and signs of ferroptosis. Prolonged exposure to hypoxia further exacerbated these effects, mirrored in human peripheral blood mononuclear cells. Single-cell sequencing showed a marked reduction in macrophage populations, affecting the spleen’s ability to clear RBCs and contributing to splenomegaly. Our findings suggest splenic ferroptosis contributes to decreased RPMs, affecting erythrophagocytosis and potentially fostering continuous RBCs production in HAPC. These insights could guide the development of targeted therapies for HAPC, emphasizing the importance of splenic macrophages in disease pathology.
Journal Article
Citrate-Assisted One-Pot Hydrothermal Preparation of Carbonated Hydroxyapatite Microspheres
Carbonated hydroxyapatite (CHA) microspheres have aroused wide concern in biofields because of their excellent biological and surface properties. However, the facile preparation of CHA microspheres from organic compounds, especially the microstructural transformation during synthesis, has been rarely reported. In this work, CHA microspheres with an average diameter of 2.528 μm and a BET surface area of 51.0658 m2/g were synthesized via a one-pot hydrothermal method at 180 °C for 10 h by using calcium chloride, diammonium hydrogen phosphate, urea, and trisodium citrate (TSC) with a molar ratio of TSC to Ca of 1:2. The effects of hydrothermal treatment temperature and molar ratio of TSC to Ca on the morphology of the products were investigated. As a chelating agent, TSC is crucial to the formation of CHA microspheres during the hydrothermal homogeneous precipitation process. A possible mechanism of the microstructural transformation from bundle to dumbbell, dumbbell ball, and finally, microspheres regulated by TSC and urea was proposed. The CHA microspheres can be used as effective drug carriers for biomedical applications.
Journal Article
Advancements in Characterizing Fiber Distribution in Fiber-Reinforced Concrete Using X-ray Computed Tomography
The distribution of fibers within fiber-reinforced concrete significantly impacts its mechanical properties. X-ray computed tomography (CT) provides a distinctive and technically proficient method for examining fiber dispersion. This paper presents an exhaustive review of the methodologies used to characterize fiber distribution in concrete. It delves into the fundamental principles of X-ray CT and its application in studying fiber distribution, highlighting the current state of research. Additionally, the study explores the influence of fiber distribution and orientation on the failure mechanisms of concrete, offering insights that could guide future investigations in this domain. The paper concludes with a discussion on the potential of X-ray CT in evaluating fiber distribution and its implications for the mechanical properties of concrete, thereby setting the stage for further advancements in the field.
Journal Article